1. Field of the Invention
The present invention relates to a method for stimulating oil wells and the surrounding formations or cleaning the well pipe. More particularly, it relates to in situ sonic stimulation of underground formations penetrated by a well hole wherein unrecoverable liquids are trapped by residual tars or within untapped cavities which can be broken up or opened by sonic energy and cleaning the interior walls of the well pipe sections of deposits from production therethrough.
2. Description of the Prior Art
Acoustic energy has been used for drilling a liquid filled borehole by periodically reducing hydrostatic pressure in the borehole and simultaneously introducing acoustic energy to effect cavitation in the liquid. Also sonic vibration of an elastic stem for taking core samples is known. Drilling of boreholes by acoustic pulses in the range of cavitation is also known. However in all drilling techniques for recovering certain hydrocarbons or other fluids from subterranean formations, a point is often reached where the remaining recoverable fluids are trapped within the reservoir by residual tars or within untapped pockets within the formation.
Many secondary recovery operations for stimulating such wells are known in the prior art. Among these are acid treatment, burning, high pressure fracturing and the like. The skilled driller will choose a method among these to stimulate a given well depending upon the conditions he believes exist within the formation. The present invention adds another secondary recovery operation to his repertoire. Further, it provides a method of cleaning the well pipe of blocking deposits thereby increasing its flow area.